A GPS (global positioning system) is a global measurement system that measures a distance between a satellite and a receiver from a propagation delay time of an electric wave to determine a position of the receiver. Recently, various satellite navigation systems such as a Galileo from Europe, QZSS from Japan, and COMPAS from China have been established other than the GPS.
Researches on a receiver design, which is a core technology on a user side, were mainly focused on a hardware GPS receiver design based on an ASIC chipset model before 2000. The hardware based receiver can advantageously realize a highly integrated multichannel correlator based on a receiver design that is specialized in an application field and an advanced ASIC design technology. In contrast, the hardware based receiver has a limitation to apply to diversified satellite navigation system because the GPS chipset needs to be re-designed in order to change the design of the receiver and improve the performance.
In order to overcome the above-mentioned disadvantages, a design of a software based GPS receiver which is a new design method has become a research topic since the late 1990s and the researches thereof have actively been conducted. Research of the software receiver design technology starts with a multipurpose communication system design technology to which an initial SDR (software defined radio) concept is applied. Generally, the software GPS receiver is designed to perform all processing processers of GPS except a RF (radio frequency)-front-end using a software module which operates in a general purpose processor. Ultimately, the software receiver design technology aims to include a software realization technology of RF-Front-End.